The NBO analysis was performed to get an insight into the interplay between pnicogen bonding and other interactions. The results of the NBO analysis are summarized in Table S2. One can see that CT is much larger in the pnicogen bond than that in the halogen bond, while it is smaller in the pnicogen bond than that in the triel bond. It is generally accepted that the larger CT corresponds to a stronger interaction^[49], although for different types of interaction there is no good correlation between CT and binding energies. It is observed that the charge transfer is reduced for both the halogen bond and pnicogen bond in X…CN-Ph-CN…PO₂F complexes, and a reverse result is found in Y…Br-Ph-CN…PO₂F complexes. It should be mentioned that in the case of BH₃…CN-Ph-CN and BH₃…CN-Ph-CN…PO₂F systems, the complexes are considered as one molecule in the NBO program, and thus the relevant charge transfer energies E ⁽²⁾were not obtained. For BF₃…CN-Ph-CN and BF₃…CN-Ph-CN…PO₂F systems, N lone pair donation occurs from the Lewis base into the empty p(π) orbital of B. The E ⁽²⁾ greatly decreases from 152.28 to 14.93 kcal/mol from dimer to the trimer, which is consistent with the increased B…N distance in the trimer in comparison with the dimer.